1. Field of the Invention
The present invention relates to an exposure equipment to fabricate a semiconductor element, a magnetic head, or the like, and a controlling method of the same.
2. Description of the Related Art
Conventionally, when fabricating a semiconductor element, a magnetic head, or the like, a lithography technology has been in use, in which a predetermined pattern is transferred onto a resist coated on a wafer surface by an exposure to light. As a system configuration to perform an exposure using a beam such as ultraviolet or laser as a lithography process, there is a lithography system of a so-called inline type, in which a resist coating equipment, exposure equipment, and the like are unified.
On the other hand, as a system configuration to perform an electron-beam exposure, there is a lithography system configured to install therein the exposure equipment and the other equipment such as the resist coating equipment separately. This lithography system is sometimes operated also when performing an exposure using the ultraviolet or laser beam. In this lithography system, the exposure equipment is configured to include an equipment to expose a wafer surface, a container such as a SMIF (Standard Mechanical Interface)-POD to contain a wafer carrier containing a wafer so as to transfer the wafer between the equipment and the other equipment, and a transfer unit having a space to transfer the wafer carrier between the container to/from the equipment and the other equipment.
In this case, the wafer and a peripheral portion thereof require extremely high cleanliness, it is therefore necessary to constantly maintain the inside of the space of the transfer unit to be clean, by providing, for example, a HEPA filter into the transfer unit to be a transfer path of the wafer so that an airflow (clean air) is generated in the transfer unit by using the HEPA filter.
In the lithography system in which an exposure equipment and the other equipment are separately installed, a wafer is exposed to an atmospheric airflow in the transfer unit during the time from the end of a resist coating step and to the start of an exposure step. In the case of an electron-beam exposure, in particular, the exposure for wafer takes an extremely long time. Therefore, when many wafers are set in a wafer carrier, those wafers to be exposed later end up to be exposed to the atmospheric airflow for hours. Depending on the waiting time, a reaction between the resist and a base or the like shows a progress, exercising an unacceptable effect on a line width of a pattern to be formed. Such a problem is becoming unignorable recently on the back of a progress in microfabrication of the semiconductor elements, in which the allowable error range related to the line width is becoming smaller.
In Japanese Patent Application Laid-Open No. Hei 7-176458 (Patent Document 1), there is disclosed a technique, in which the repeatability of an exposed pattern is controlled by controlling a time from post-exposure to pre-development in relation to the resist on the wafer surface. However, even with this technique, it is extremely difficult to suppress the line width fluctuation of the pattern, once the resist suffers deterioration caused by a long-time exposure to the airflow.